The United Nations has called on the Croatian government to investigate allegations of police abusing migrants and asylum seekers, including claims officers have started humiliating asylum seekers by spray-painting crosses on their heads.

The U.N.'s refugee agency, UNHCR, confirmed to Newsweek on Wednesday that it had asked the Croatian government to investigate concerns raised over reports of police carrying out abuses against migrants and asylum seekers at the Croatian border amid the coronavirus pandemic.

In photos published in a recent report by the Border Violence Monitoring Network, a European migration watchdog organization, as well as by British newspaper The Guardian, several men can be seen with their heads spray-painted with crosses.

According to the BVMN report, titled COVID-19 and Border Violence Along the Balkan Route, the men claim to be asylum seekers who say Croatian police spray-painted the crosses after they were caught trying to enter the country from Bosnia outside designated ports of entry.

The cases, the report states, were documented by No Name Kitchen (NNK), a non-governmental organization operating in Velika Kladu?a, a town located in the far northwest of Bosnia and Herzegovina, near the border of Croatia.

Calling the incidents a "relatively new development in pushback practices," the report says NKK had identified at least two cases in the first week of May where "transit groups returned with spray paint markings administered to their clothes and exposed [areas]."

Speaking with Newsweek on Thursday, Simon Campbell, a field coordinator with the Border Violence Monitoring Network, said the use of spray paint appeared to be a means of humiliating asylum seekers.

"Even though the spray paint can obviously irritate skin and eyes...the whole act of marking or branding someone is an act of humiliation or degrading, inhumane treatment," he said.

"This kind of approach is what you would see farmers doing to cattle and livestock rather than doing to human beings," he said.

Speaking with The Guardian, Jack Sapoch, a representative of NKK, also accused Croatian authorities of trying to humiliate asylum seekers with the orange markings.

"It is obvious that one of the intended effects of this behavior is to humiliate refugees and migrants attempting to cross the border," Sapoch said.

With the spray-painted markings appearing to resemble crosses, Sapoch suggested that the markings could be intended to "traumatize" Muslim asylum seekers in particular.

"As far as I see it, this is the result of either one of two motivations. Either the Croatian authorities committing these acts are using spray paint to identify and humiliate repeat border crossers or, more worryingly, they are using this as a tactic to psychologically traumatize these men—the majority of whom are Muslim—with a religious symbol," Sapoch said.

The new development comes as Croatian police continue to be accused of violence against migrants and asylum seekers caught crossing the country's border.

In a statement sent to Newsweek, Zoran Stevanovi?, the UNHCR regional communications officer for central Europe, said the "UNHCR has been receiving for some time credible reports of people who claim they have been unlawfully returned from Croatia to Bosnia and Herzegovina and Serbia and has shared them with the authorities."

"These reports highlight problems regarding the identification of asylum claims, access to the territory, violence and excessive use of force, identification of vulnerable individuals, including unaccompanied children, etc.," Stevanovi?, said.

"UNHCR is deeply concerned about these reports and has requested the Croatian government to investigate all claims of denied access to territory and of violations and abuse and to establish an independent assessment mechanism to establish the facts of the border situation," he said.

The UNHCR spokesperson also specifically confirmed that the UNHCR was aware of the spray-painting incidents, asserting that the "UNHCR in Bosnia Herzegovina did learn about the allegations through partners working in the field."

"UNHCR considers that all countries have a legitimate right to control their borders and manage irregular movements, but they also have an obligation under international law to assess the claims of people who seek asylum and to ensure that these individuals can access asylum procedures," Stevanovi? said.

"Migrants and asylum-seekers also have duties and obligations to respect national laws and measures to maintain public order, including being obliged to cooperate with the asylum authorities," he said, adding: "Effective border management is not incompatible with responding to the rights of asylum seekers."

Newsweek has contacted Croatian authorities for comment.

This article has been updated with statements from Simon Campbell, a field coordinator with the Border Violence Monitoring Network.

A group of migrants walk on a dusty track through a wooded area in the countryside, near Bosanska Krupa, in Northern Bosnia, on July 3, 2019, after being physically expelled by police from neighboring Croatia for attempting to cross the border. Croatian authorities have been accused of abuse against migrants and asylum seekers caught crossing the border.ELVIS BARUKCIC/AFP/Getty